Current methods used for retracting tissue and improving visualization and working space include mechanical separation using metal retractors during surgery, balloon retractors, and direct pressure of an unconfined flow of fluid such as water or CO.sub.2 during surgery. A number of retractors have been disclosed and, in the interest of brevity, will not be further described here. The reader is referred to Bonutti, U.S. Pat. No. 5,197,971, Bonutti, U.S. Pat. No. 5,295,994, Bonutti, U.S. Pat. No. 5,345,927, and Moll et al., U.S. Pat. No. 5,309,896, these and all other references cited in this document are expressly incorporated by reference as if fully set forth herein in their entirety. Tissue dissection has also been discussed and, for general considerations, the reader is referred to Bonutti, U.S. Pat. No. 5,163,949, Kieturakis, International Publication No. WO95/32663, Kieturakis et al., EP 0,573,273 A2, published Dec. 8, 1993, Kieturakis et al., International Publications No. WO96/00531, published Jan. 11, 1996, and Fogarty et al., International Publication No. WO96/00597, published Jan. 11, 1996.
Tissue retractors have been particularly useful in orthopedic surgery. There are several orthopedic procedures which have the potential to offer both low cost and patient benefit. Among these is spinal fusion. There are about 200,000 such procedures performed annually in the United States. In general, the procedure is performed to eliminate a ruptured vertebral disk which is causing significant patient discomfort, and subsequently to promote fusion between the then-exposed and adjacent vertebra. This fusion can be promoted by any of several proprietary prosthetic systems or by traditional bone prostheses, or by a combination of the two. Most traditional systems have utilized a posterior approach to the spine.
Several newer systems, some currently under investigation have utilized an anterior approach, and seem to promise better clinical results. The open anterior approach is highly invasive, however, and has led researchers to try a transperitoneal laparoscopic variation to the open procedure. This is an improvement, but still subjects the patient to those same risks associated with invasion of the peritoneum outlined above, but if anything, more severely.
There have recently been several cadaver studies where an extraperitoneal laparoscopic approach to the lumbar spine has been attempted with success. This is a natural target procedure since the dissected space required is essentially the same as that required for aortic reconstruction. Most interesting is that the space dissection requirements are largely the same for all of the prosthetic systems under study.